There are conventionally-known fluorescence viewing devices configured to supply and apply excitation light of a predetermined wavelength to an observed object and acquire an observed image of fluorescence generated in the observed object, by an imaging device. Such fluorescence viewing devices are used, for example, for identification of living tissue such as a lymph vessel or a lymph node in medical fields. When the fluorescence viewing is performed to observe temporal change of states of the observed object or the like, a method to be used is one to acquire images in a time series at a predetermined frame rate and observe a moving picture of the observed object (e.g., cf. Patent Literatures 1 and 2).